Sending a trigger pulse by RF

[Pimpom]

I'd like to send a simple trigger pulse by RF at irregular intervals
(seconds to minutes). No other data need be sent. No special requirement on
the length or type of trigger signal. All that's needed is something like
the momentary pressing of a light switch. The triggered device will be
locally reset in between each triggered event.

The transmission distance is roughly half a kilometer in unobstructed
line-of-sight. I'm thinking of using some readymade transceiver modules,
perhaps in the 2.4GHz band, so the RF portions are not really part of my
question. My main concerns are -

1. Delay between transmission and trigger output from the receiver should be
less than 1 msec
2. Avoiding false triggering by RF interference sources like vehicles,
cellphones and other spurious sources.

What approach do you suggest to satisfy the above requirements? For example,
will a tone burst transmission and a tone decoder at the Rx be sufficient?
Thanks in advance.

 

[Sjouke Burry]

Pimpom wrote:

I'd like to send a simple trigger pulse by RF at irregular intervals
(seconds to minutes). No other data need be sent. No special requirement on
the length or type of trigger signal. All that's needed is something like
the momentary pressing of a light switch. The triggered device will be
locally reset in between each triggered event.

The transmission distance is roughly half a kilometer in unobstructed
line-of-sight. I'm thinking of using some readymade transceiver modules,
perhaps in the 2.4GHz band, so the RF portions are not really part of my
question. My main concerns are -

1. Delay between transmission and trigger output from the receiver should be
less than 1 msec
2. Avoiding false triggering by RF interference sources like vehicles,
cellphones and other spurious sources.

What approach do you suggest to satisfy the above requirements? For example,
will a tone burst transmission and a tone decoder at the Rx be sufficient?
Thanks in advance.


If you have a direct line of sight, why not try for infrared?

The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.
I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a cheap
AM radiochip. There are cheap ones on the market, to cannibalize.

 

[Phil Hobbs]

Sjouke Burry wrote:

Pimpom wrote:
I'd like to send a simple trigger pulse by RF at irregular intervals
(seconds to minutes). No other data need be sent. No special
requirement on the length or type of trigger signal. All that's needed
is something like the momentary pressing of a light switch. The
triggered device will be locally reset in between each triggered event.

The transmission distance is roughly half a kilometer in unobstructed
line-of-sight. I'm thinking of using some readymade transceiver
modules, perhaps in the 2.4GHz band, so the RF portions are not really
part of my question. My main concerns are -

1. Delay between transmission and trigger output from the receiver
should be less than 1 msec
2. Avoiding false triggering by RF interference sources like vehicles,
cellphones and other spurious sources.

What approach do you suggest to satisfy the above requirements? For
example, will a tone burst transmission and a tone decoder at the Rx
be sufficient? Thanks in advance.


If you have a direct line of sight, why not try for infrared?
The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.
I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a cheap
AM radiochip. There are cheap ones on the market, to cannibalize.

Infrared is far harder due to the solar background. You can do it at
night, but in the daytime, 500 metres is hard. Also out in Pimpom's
neighbourhood the airwaves are probably a lot clearer than where you are!

With a nice narrow bandwidth signal like that, Pimpom could use the AM
band with a multi-turn loop antenna on each end.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

 

[Pimpom]

Sjouke Burry wrote:

Pimpom wrote:
I'd like to send a simple trigger pulse by RF at irregular
intervals
(seconds to minutes). No other data need be sent. No special
requirement on the length or type of trigger signal. All
that's
needed is something like the momentary pressing of a light
switch.
The triggered device will be locally reset in between each
triggered
event. The transmission distance is roughly half a kilometer
in unobstructed
line-of-sight. I'm thinking of using some readymade
transceiver
modules, perhaps in the 2.4GHz band, so the RF portions are
not
really part of my question. My main concerns are -

1. Delay between transmission and trigger output from the
receiver
should be less than 1 msec
2. Avoiding false triggering by RF interference sources like
vehicles, cellphones and other spurious sources.

What approach do you suggest to satisfy the above
requirements? For
example, will a tone burst transmission and a tone decoder at
the Rx
be sufficient? Thanks in advance.


If you have a direct line of sight, why not try for infrared?

Thanks for the reply. But IR at 500m? Is it feasible?

The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.

That's my biggest concern. I'll go for encoding as a last resort,
but would like to avoid it if a reasonably simple alternative is
available.

I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a cheap
AM radiochip. There are cheap ones on the market, to
cannibalize.

Can you point me to an example of practical applications of this
technique at comparable distances? If this were for a fixed
installation, I'd go for a cable system - copper or fiber optic.
But the application is to be used only a few times a year,
transported outside town, set up and dismantled after each use.

 

[Pimpom]

Phil Hobbs wrote:

Sjouke Burry wrote:
Pimpom wrote:
I'd like to send a simple trigger pulse by RF at irregular
intervals
(seconds to minutes). No other data need be sent. No special
requirement on the length or type of trigger signal. All
that's
needed is something like the momentary pressing of a light
switch.
The triggered device will be locally reset in between each
triggered event. The transmission distance is roughly half a
kilometer in
unobstructed line-of-sight. I'm thinking of using some
readymade
transceiver modules, perhaps in the 2.4GHz band, so the RF
portions
are not really part of my question. My main concerns are -

1. Delay between transmission and trigger output from the
receiver
should be less than 1 msec
2. Avoiding false triggering by RF interference sources like
vehicles, cellphones and other spurious sources.

What approach do you suggest to satisfy the above
requirements? For
example, will a tone burst transmission and a tone decoder at
the Rx
be sufficient? Thanks in advance.


If you have a direct line of sight, why not try for infrared?
The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.
I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a
cheap
AM radiochip. There are cheap ones on the market, to
cannibalize.

Infrared is far harder due to the solar background. You can do
it at
night, but in the daytime, 500 metres is hard.

I'd think so too. I've used IR with standard remote control
receivers at much shorter ranges (up to ~15 metres in direct
sunlight), but what Sjouke proposes is an entirely different
matter.

Also out in Pimpom's
neighbourhood the airwaves are probably a lot clearer than
where you
are!

Probably! But I wouldn't want to depend too much on that.

With a nice narrow bandwidth signal like that, Pimpom could use
the AM
band with a multi-turn loop antenna on each end.

To use the AM band with that range, I'll probably have to break a

few laws. Not that there's much danger of anyone in authority
noticing it. But I was thinking of using an approved commercial
module, beamed with yagi antennas at both ends. I've made and
used yagis for other purposes at VHF, but not at the higher UHF
freqs.

 

[Phil Hobbs]

Pimpom wrote:

Phil Hobbs wrote:
Sjouke Burry wrote:
Pimpom wrote:
I'd like to send a simple trigger pulse by RF at irregular
intervals
(seconds to minutes). No other data need be sent. No special
requirement on the length or type of trigger signal. All
that's
needed is something like the momentary pressing of a light
switch.
The triggered device will be locally reset in between each
triggered event. The transmission distance is roughly half a
kilometer in
unobstructed line-of-sight. I'm thinking of using some
readymade
transceiver modules, perhaps in the 2.4GHz band, so the RF
portions
are not really part of my question. My main concerns are -

1. Delay between transmission and trigger output from the
receiver
should be less than 1 msec
2. Avoiding false triggering by RF interference sources like
vehicles, cellphones and other spurious sources.

What approach do you suggest to satisfy the above
requirements? For
example, will a tone burst transmission and a tone decoder at
the Rx
be sufficient? Thanks in advance.


If you have a direct line of sight, why not try for infrared?
The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.
I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a
cheap
AM radiochip. There are cheap ones on the market, to
cannibalize.

Infrared is far harder due to the solar background. You can do
it at
night, but in the daytime, 500 metres is hard.

I'd think so too. I've used IR with standard remote control
receivers at much shorter ranges (up to ~15 metres in direct
sunlight), but what Sjouke proposes is an entirely different
matter.

Also out in Pimpom's
neighbourhood the airwaves are probably a lot clearer than
where you
are!

Probably! But I wouldn't want to depend too much on that.


With a nice narrow bandwidth signal like that, Pimpom could use
the AM
band with a multi-turn loop antenna on each end.

To use the AM band with that range, I'll probably have to break a
few laws. Not that there's much danger of anyone in authority
noticing it. But I was thinking of using an approved commercial
module, beamed with yagi antennas at both ends. I've made and
used yagis for other purposes at VHF, but not at the higher UHF
freqs.

100 mW in the AM band is legal most places, I think, and that would work
with a narrow enough bandwidth--e.g. a 1 MHz crystal osc at one end and
a matching crystal at the other. (You'd have to make sure the load
capacitance was the same at both ends too, of course.)

Depending on how fancy you want to get, there are more commercial
approaches...a wifi bridge and a couple of Yagis would get you data
communications end to end.

The nice thing about low frequencies is that you get good reception with
simpler antennas--the higher you go, the more antenna gain you have to
use to keep the same intercepted area (i.e. the same RX power).


Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

 

[Jon Kirwan]

On Sat, 25 Dec 2010 22:58:47 +0530, "Pimpom"
<Pimpom@invalid.net> wrote:

Sjouke Burry wrote:

snip

If you have a direct line of sight, why not try for infrared?

Thanks for the reply. But IR at 500m? Is it feasible?
snip

I certainly haven't tried it, but I can suggest some thoughts
to consider about the idea. The sun travels across the sky
and you probably cannot select your direction from xmtr to
rcvr. So there is probably some "worst case" situation with
the sun in the sky that you can't do a lot about. But you
can do some things, I think.

One of them is to figure out ways to limit the bandwidth in
optical wavelength and modulation frequency and limit the
field of view of the receiver, since you have line of sight.
Your source might be broadband (xenon strobe?) but you can
limit the received optical wavelength to some very narrow
band using optical filters. This will exclude a lot of light
from the sun. What you will then need to do is somehow make
the transmitter emit enough against that background to at
least make a PLL function, which can certainly "find lock" at
night time and perhaps hold it during the day. Which is the
next thing -- using a precision modulation frequency on the
transmitter ... as precise as possible ... and use as narrow
as possible acceptance filtering on the receiver. The sun's
energy will be spread out (perhaps there are some low energy
frequencies at whatever wavelength you limit yourself to) and
the narrower you can make this the less energy from the sun
you need to deal with during the day. And of course there
are optical means (long tube, telescope, baffling, etc) that
you can do with the receiver, as well. These can be more
restrictive in one plane than another (vertical vs
horizontal, for example.)

Perhaps a combination of these could get you there?

Then there may be some problem with human dangers from your
emitters. I don't know.

Just thinking out loud about this:

(1) Laser emitters, because of their narrower bandwidth (and
especially gas lasers instead of diode versions), would be
preferred because they can benefit better from thin film
narrow band optical filters as well as provide much better
point-to-point directivity (lower divergence) and in the end
reject more of the background illumination from the sun. (You
don't need the higher modulation bandwidth, necessarily, but
lasers will probably allow you more options there, too.) In
short, I'd probably first look into the selection of
appropriate laser diode emitters (cheaper than gas), but
wavelength may be a factor in making choices.

(2) Weather, rain, fog, smog, some wild animal standing in
the beam for all I know, may affect things aversely. I've no
idea here.. but you need to think about it.

(3) Collimated emitter is wise together with the use of a
very narrow field of view for the receiver. (Keep in mind
reflections that bang around and wise use of baffling and
absorptive coatings on the baffling parts -- at whatever
wavelength you choose to rely upon.)

(4) The sun path, given your two locations, may inevitably
overwhelm whatever you do with narrow receiver FOV, etc. So
you may not be able to avoid disruption at certain times.

(5) Avalanche detectors are more sensitive than PIN, I
gather, so that may help with a transimpedance amp over
distance. But solar radiation may saturate the system, so
this brings back in making an amplifier front end that
attenuates DC signal (and anything 'out of band') as much as
possible. I've read that InGaAs APDs operating at 1.55
micron might help, versus those operating in the usual 780 to
850 nm, which are probably more influenced by solar
illumination when taking into account variations in the
background levels. I don't know, though.

(6) Modulation and limiting acceptance at the receiver is
likely very important to achieve final success and lock out
still more of the solar illumination.

I've also probably failed to think of something important.

All this seems to suggest RF. Too many different facets to
worry about and get right with IR. But you did say "line of
sight" so maybe it is doable??

Oh, well. Interesting to at least consider for a moment.

Jon

 

[Sjouke Burry]

Pimpom wrote:

Sjouke Burry wrote:
Pimpom wrote:
I'd like to send a simple trigger pulse by RF at irregular
intervals
(seconds to minutes). No other data need be sent. No special
requirement on the length or type of trigger signal. All
that's
needed is something like the momentary pressing of a light
switch.
The triggered device will be locally reset in between each
triggered
event. The transmission distance is roughly half a kilometer
in unobstructed
line-of-sight. I'm thinking of using some readymade
transceiver
modules, perhaps in the 2.4GHz band, so the RF portions are
not
really part of my question. My main concerns are -

1. Delay between transmission and trigger output from the
receiver
should be less than 1 msec
2. Avoiding false triggering by RF interference sources like
vehicles, cellphones and other spurious sources.

What approach do you suggest to satisfy the above
requirements? For
example, will a tone burst transmission and a tone decoder at
the Rx
be sufficient? Thanks in advance.


If you have a direct line of sight, why not try for infrared?

Thanks for the reply. But IR at 500m? Is it feasible?

The radioband is extremely polluted, and unless you protect
your connection with encoded fingerprinting, like they do
with a garage door opener, you will get very frequent unwanted
triggering.

That's my biggest concern. I'll go for encoding as a last resort,
but would like to avoid it if a reasonably simple alternative is
available.

I would try a bunch of IR diodes, modulated with say 1MHZ,
and a receiving diode connected to the antenna input of a cheap
AM radiochip. There are cheap ones on the market, to
cannibalize.

Can you point me to an example of practical applications of this
technique at comparable distances? If this were for a fixed
installation, I'd go for a cable system - copper or fiber optic.
But the application is to be used only a few times a year,
transported outside town, set up and dismantled after each use.


When you can use a fixed path, you can shield the receiving diode

with say a 1 yard 2inch pipe, the inside painted with black non-glossy
paint. That takes care of most of the daylight.
Modulating the transmitted beam takes care of the rest of the
static light, because of ac amplification.
We did something like that years ago, with transmittor consisting of
a 100 diode square.
Today I would use a laser diode, they are quite powerfull these days.
For a range measurement I used a 80 amp IR diode with a pulse length
of 4 Nanosec, 10 times/sec.
That was enough for a distance of ~40 meters, with passive reflection,
so reduced by the fourth power of the distance.
Such a diode, at a lower current and 50% dutycycle, 1Mhz,
should have no problem with the distance, but you need a colimator?
lense.
The receiving diode would need to be a wide area optical diode.
Both diodes are EXPENSIVE.
This is from memory, I dont work there anymore, for more info try google.

 

[Rich Grise]

Pimpom wrote:

To use the AM band with that range, I'll probably have to break a
few laws. Not that there's much danger of anyone in authority
noticing it. But I was thinking of using an approved commercial
module, beamed with yagi antennas at both ends. I've made and
used yagis for other purposes at VHF, but not at the higher UHF
freqs.

This is the one that gets my vote - if you really have LOS, then
it should be trivial, especially if you can afford to buy rather
than build.

Cheers!
Rich

 

[Pimpom]

Rich Grise wrote:

Pimpom wrote:

To use the AM band with that range, I'll probably have to
break a
few laws. Not that there's much danger of anyone in authority
noticing it. But I was thinking of using an approved
commercial
module, beamed with yagi antennas at both ends. I've made and
used yagis for other purposes at VHF, but not at the higher
UHF
freqs.

This is the one that gets my vote - if you really have LOS,
then
it should be trivial, especially if you can afford to buy
rather
than build.

There will definitely be LoS, with flat open ground along the

Tx-Rx path and trees and power lines some tens of metres running
parallel on each side. Transceiver modules intended for serial
data transmission with stated ranges of 1-3 km in optimal
conditions are not all that expensive even here in India.

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.

 

[Jamie]

Pimpom wrote:

Rich Grise wrote:

Pimpom wrote:

To use the AM band with that range, I'll probably have to
break a
few laws. Not that there's much danger of anyone in authority
noticing it. But I was thinking of using an approved
commercial
module, beamed with yagi antennas at both ends. I've made and
used yagis for other purposes at VHF, but not at the higher
UHF
freqs.

This is the one that gets my vote - if you really have LOS,
then
it should be trivial, especially if you can afford to buy
rather
than build.


There will definitely be LoS, with flat open ground along the
Tx-Rx path and trees and power lines some tens of metres running
parallel on each side. Transceiver modules intended for serial
data transmission with stated ranges of 1-3 km in optimal
conditions are not all that expensive even here in India.

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.


you need a coded signal because just the carrier alone may give

you false triggers.

One could use a date carrier Transceiver and encode a serial
stream to be read and decoded. If CRC passes along with Key code, then
it can send it's pulse to the device.. The system should send a ACK back
to the transmitter to validate that it did receive it.. Otherwise, you
may want to try again, if it applies.. This could be done at high
speed but there will be a delay and this has to be factored in..

Sending a continous carrier with a low freq PLL signal on the carrier
most likely will work better. This way the receiver will be desensed due
to your close TX unit and constantly in lock with the PLL freq on the
carrier, a slight shift on this tone can generate a Phase shift at the
RX end very quickly and the phase detect can be used to generate the pulse.

Jamie



--
"I'd rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

 

[Rich Grise]

Pimpom wrote:

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.

Well, depending on your resources, you could do some sort of
handshaking, if you can have T/R at both ends:

1. TX: "I have a signal!"
2. RX: "OK, I'm ready."
3. TX: "Here ya go!"
4a. RX: "Got it!"
execute task, go back to wait loop
4b: RX: "didn't get it."
Send NAK, wait for resend
5: Loop forever ;-)

Cheers!
Rich

 

[Rich Grise]

Jamie wrote:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT

THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

Speaking of Slinkies, has anyone ever pushed a Slinky down an up
escalator? ;-)

Cheers!
Rich

 

[Grant]

On Sun, 26 Dec 2010 15:22:09 -0800, Rich Grise <richg@example.net.invalid> wrote:

Pimpom wrote:

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.

Well, depending on your resources, you could do some sort of
handshaking, if you can have T/R at both ends:

1. TX: "I have a signal!"
2. RX: "OK, I'm ready."
3. TX: "Here ya go!"
4a. RX: "Got it!"
execute task, go back to wait loop
4b: RX: "didn't get it."
Send NAK, wait for resend
5: Loop forever ;-)

You can do one-way reliable signaling, just make sure there's lots of
redundancy sent, and that the receiver ignores event duplication. I
spent a decade doing that sort of stuff for security systems where
false alarms are as bad as not receiving an alarm. It's quite easy to
implement the concept with today's toys.

Grant.

Cheers!
Rich

 

[krw@att.bizzzzzzzzzzzz]

On Mon, 27 Dec 2010 10:40:39 +1100, Grant <omg@grrr.id.au> wrote:

On Sun, 26 Dec 2010 15:22:09 -0800, Rich Grise <richg@example.net.invalid> wrote:

Pimpom wrote:

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.

Well, depending on your resources, you could do some sort of
handshaking, if you can have T/R at both ends:

1. TX: "I have a signal!"
2. RX: "OK, I'm ready."
3. TX: "Here ya go!"
4a. RX: "Got it!"
execute task, go back to wait loop
4b: RX: "didn't get it."
Send NAK, wait for resend
5: Loop forever ;-)

You can do one-way reliable signaling, just make sure there's lots of
redundancy sent, and that the receiver ignores event duplication. I
spent a decade doing that sort of stuff for security systems where
false alarms are as bad as not receiving an alarm. It's quite easy to
implement the concept with today's toys.

Transmit time-'til-event. Receiver loads time-'til-event into a counter on
each receipt. Make timer and transmission as accurate as needed. So what if
a packet gets dropped?

 

[Jamie]

Rich Grise wrote:

Jamie wrote:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

Speaking of Slinkies, has anyone ever pushed a Slinky down an up
escalator? ;-)

Cheers!
Rich

oops, I slipped, I usually delete that in most post..

Jamie

 

[Jamie]

Rich Grise wrote:

Pimpom wrote:

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.


Well, depending on your resources, you could do some sort of
handshaking, if you can have T/R at both ends:

1. TX: "I have a signal!"
2. RX: "OK, I'm ready."
3. TX: "Here ya go!"
4a. RX: "Got it!"
execute task, go back to wait loop
4b: RX: "didn't get it."
Send NAK, wait for resend
5: Loop forever ;-)

Cheers!
Rich



I am curious what is so critical with the 1ms timing response ?

Must be something that needs to be synched?


Jamie

 

[Rich Grise]

Jamie wrote:

Rich Grise wrote:
Jamie wrote:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

Speaking of Slinkies, has anyone ever pushed a Slinky down an up
escalator? ;-)

oops, I slipped, I usually delete that in most post..

You did, or at least you did put a sig delimiter there - It didn't
get quoted in my "reply" pane; I had to copy/paste it.

I just wanted to ask about the Slinky thing, i.e., has anybody ever
pushed a Slinky down an up escalator?

I'd think you'd need a larger than normal Slinky.

Cheers!
Rich

 

[Pimpom]

Jamie wrote:

Rich Grise wrote:

Pimpom wrote:

My main concern is with avoiding false triggering due to
interference, and this is where I'm seeking opinions and
suggestions from those with experience in this area.


Well, depending on your resources, you could do some sort of
handshaking, if you can have T/R at both ends:

1. TX: "I have a signal!"
2. RX: "OK, I'm ready."
3. TX: "Here ya go!"
4a. RX: "Got it!"
execute task, go back to wait loop
4b: RX: "didn't get it."
Send NAK, wait for resend
5: Loop forever ;-)

Cheers!
Rich



I am curious what is so critical with the 1ms timing response ?

Must be something that needs to be synched?

Part of a system involving a timer. Max resolution 1ms. START

signal local to the RTC, STOP signal by the remote trigger.
(Just have time to dash that one off. Lots of social obligations.
Will reply to the other posts later. Sorry).

 

[Michael A. Terrell]

Rich Grise wrote:

Jamie wrote:
Rich Grise wrote:
Jamie wrote:

SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"

Speaking of Slinkies, has anyone ever pushed a Slinky down an up
escalator? ;-)

oops, I slipped, I usually delete that in most post..

You did, or at least you did put a sig delimiter there - It didn't
get quoted in my "reply" pane; I had to copy/paste it.

I just wanted to ask about the Slinky thing, i.e., has anybody ever
pushed a Slinky down an up escalator?

I'd think you'd need a larger than normal Slinky.

More important: Why hasn't anyone pushed Jamie off a cliff? Will he
bounce from the helium in his head, or just leave a square mile of brown
stain?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!